algebra precalculus – I have seen “Thunderbirds”. One mile away – 1/4″ long from my perspective. How big were they actually?

How big is an object actually – if I am a mile away from it and it appears to be 1/4 ” in length ?
I am standing outside looking up at a 45 degree angle towards a huge wall of storm clouds that are a mile away. Ahead of these clouds is a flock of birds that are 1/4 ” in length. These were what I believe were the fabled “THUNDERBIRDS”. I am 64 years old, have lived on an air force base for 20 of those years, and the last 35 – near an airport. These objects were not planes, and were not in the airports flight path, but they appeared to be the size of a 747. They were huge and flying side by side @ twice their size apart.
The Indians say the thunderbirds fly ahead of storms – which is what they were doing. I am now a believer. How big were they ?